Ovarian carcinoma remains the cancer with the highest mortality rate among the gynecological malignancies, with 25,400 new cancer cases estimated in 2003 in the United States alone. Ovarian serous papillary carcinoma (OSPC) is the most common histologic type of ovarian carcinoma. Because of the insidious onset of the disease and the lack of reliable screening tests, two-thirds of patients have advanced disease when diagnosed; and although many patients with disseminated tumors respond initially to standard combinations of surgical and cytological therapy, nearly 90% will develop recurrence and succumb to their disease.
Uterine cancer is the most prevalent gynecological tumor in women, with an estimated 40,100 cases and 6,800 deaths in the United States in 2003. On the basis of clinical and histopathological variables, two subtypes of endometrial carcinoma, Type I and II tumors, have been described (1,2). Type I endometrial cancers, which account for about 80% of cases, are usually well differentiated and endometrioid in histology. They are diagnosed predominantly in younger women, and have a favorable prognosis. Type II endometrial cancers are poorly differentiated tumors, often with serous papillary or clear cell histology. Although type II tumors account for only a minority of endometrial carcinoma cases, about 50% of all relapses occur in this group.
Uterine serous papillary carcinoma (USPC) tumors represent the most aggressive variant of Type II endometrial cancer and may constitute up to 10% of endometrial tumors (3-10). The microscopic criteria for diagnosis of USPC were first outlined by Hendrickson in 1982 (10). Typically, the neoplastic epithelium is characterized by serous differentiation with psammoma bodies present and with predominantly papillary architecture (11). Pleomorphism, grade III nuclear atypia with prominent nucleoli and vesicular chromatin pattern, as well as a high mitotic activity are commonly detected in this tumor. Clinically, USPC has a propensity for intraabdominal and lymphatic spread even at presentation and is characterized by a highly aggressive biologic behavior (3-10, 12). USPC is a chemoresistant disease from onset, with responses to combined cisplatinum-based chemotherapy of about 20% and short duration (7-9). The survival rate is dismal, even when USPC is only a minor component of the histologically more common endometrioid adenocarcinoma, and widespread metastasis and high mortality may occur even in those cases in which tumor is confined to the endometrium or to an endometrial polyp (4, 6, 12). The overall 5-year survival is about 30% for all stages and the recurrence rate after surgery is extremely high (50% to 80%).
Pancreatic cancer is the fifth leading cause of cancer death in the U.S. and has one of the highest mortality rates of any malignancy.
Chemotherapy resistance is a major problem in treatment of ovarian, uterine, and pancreatic cancers, and other cancers. Often a patient initially responds to chemotherapy, but the tumor develops resistance and recurs. New treatments for chemotherapy resistant tumors are needed.
Claudin-3 and claudin-4 are proteins found on the surface of cells of various tissue types involved in tight junctions connecting one cell to the adjacent cells (13). Claudins 3 and 4 have been found to be the receptors for Clostridium perfringens enterotoxin, a bacterial toxin that causes food poisoning (14-16).
Claudin-3 mRNA is expressed in normal prostrate, colon, small bowel, and pancreas (17). Claudin-4 is expressed at high levels in colon, and at moderate levels in prostate, placenta, lung, pancreas, and lower levels in small bowel, kidney, and uterus (17). Claudin-3 mRNA expression in prostate adenocarcinoma was found to be equal to or greater than expression in surrounding normal prostate tissue (17). The prostate cancer cells in tissue culture were sensitive to killing by Clostridium perfringens enterotoxin (CPE) (17).
In another report, claudin-4 mRNA was found to be not expressed or weakly expressed in normal pancreas, but was highly expressed in most primary pancreatic carcinoma samples (18). Claudin-4 expression was also found in colon cancer, breast cancer, and gastric cancer samples (18). CPE was reported to kill pancreatic cancer cell lines in vitro (18). Pancreatic tumor xenografts were induced in nude mice, and the tumors were directly injected with CPE over the course of 5 days. The CPE-treated tumors showed no increase in size and exhibited areas of necrosis, while the untreated tumors grew (18).
Hough et al. reported results of serial analysis of gene expression (SAGE) comparing expression of genes in ovarian surface epithelium, cystadenoma, and ovarian primary tumors (19). Many genes were found to be upregulated in ovarian tumors compared to normal ovarian epithelium. Several of these were surface proteins. Surface proteins shown to be upregulated included claudin-3 and -4, HE4, mucin-1, epithelial cellular adhesion molecule, and mesothelin (19). Claudin-3 and -4 mRNA and protein levels were also reported to be elevated in ovarian carcinoma samples as compared to normal ovarian tissue and ovarian cystadenoma (20).
New methods for treating cancer are needed. Methods for treating the most deadly cancers, including ovarian cancer, pancreatic cancer, and uterine serous papillary carcinoma, are particularly needed. Methods for treating chemotherapy resistant cancers are particularly needed. Preferably the methods would have reduced side effects and involve reduced toxicity for healthy non-target tissue.